Following the above mentioned rant, there's been expressed interest by Mozilla, Opera and Facebook to agree on specifying a format in JSON which would be compatible with the existing Widget Spec. There's even an existing proposal by Rich Tibbett on how to do that.

What's even better, the WebApps group's just carved out a space for it in its proposed charter:

Widgets Packaging and XML Configuration

A packaging format and configuration format for widgets. The group may choose to update this work with other packaging and/or configuration syntax specifications, such as a JSON or plain-text format.